5-HYDROXYINDOLEACETIC ACID EXCRETION FOLLOWING COMBINATION CHEMOTHERAPY WITH CYCLOPHOSPHAMIDE, EPIRUBICIN AND 5-FLUOROURACIL PLUS ONDANSETRON COMPARED TO ONDANSETRON ALONE

The aim of the work was to evaluate the impact of cyclophosphamide and ondansetron on serotonin metabolism measured by urinary 5-hydroxyindo leacetic acid (5-HIAA) excretion. The pattern of urinary 5-HIAA excret ion was analysed within 24 h following cyclophosphamide, epirubicin an d 5-fluorouracil (FEC) chemotherapy (n = 14), ondansetron as single ag ent (n = 31), and in a control group (n = 62). 5-HIAA was measured by a fluorescence/polarisation immunoassay. Both FEC and ondansetron alon e induced a significantly higher 5-HIAA increase following the first 1 2 h after drug administration when compared to the control group. The comparison of quantitative variables of 5-HIAA excretion between FEC a nd ondansetron failed to reveal any statistical differences. Cyclophas phamide-based chemotherapy is associated with only minor increases of 5-HIAA excretion, Analysis of 5-HIAA excretion does not help in the de scription of the pathophysiology of cyclophssphamide-induced emesis. I n contrast to experimental data, serotonin 3 receptor antagonism with ondansetron induces an increase of 5-HIAA excretion in humans.